U.S. patent number 4,262,062 [Application Number 06/133,212] was granted by the patent office on 1981-04-14 for metal-air battery with environment control for intermittent high current demand.
This patent grant is currently assigned to Timex Corporation. Invention is credited to Norman Zatsky.
United States Patent |
4,262,062 |
Zatsky |
April 14, 1981 |
Metal-air battery with environment control for intermittent high
current demand
Abstract
An air/metal cell includes an internal gas-permeable membrane to
restrict the transfer of oxygen from ambient atmosphere to the
cathode, and incorporates an internal valve actuated by external
force on the cell to open the valve and admit substantial
quantities of oxygen for intermittent high current drain on the
cell. Preferably the external force is provided by the same
switching device which closes the electric circuit requiring the
high current drain. The cell is specifically shown in the
environment of a zinc/air cell powering a digital wristwatch. The
high current mode of the cell is actuated by the pushbutton of the
watch which turns on a miniature lamp.
Inventors: |
Zatsky; Norman (Southbury,
CT) |
Assignee: |
Timex Corporation (Waterbury,
CT)
|
Family
ID: |
22457504 |
Appl.
No.: |
06/133,212 |
Filed: |
March 24, 1980 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
|
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66203 |
Aug 13, 1979 |
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Current U.S.
Class: |
429/407; 429/444;
429/72; 429/110; 968/503 |
Current CPC
Class: |
H01M
50/216 (20210101); H01M 6/50 (20130101); H01M
12/06 (20130101); G04C 10/00 (20130101) |
Current International
Class: |
H01M
12/06 (20060101); H01M 2/10 (20060101); H01M
6/00 (20060101); H01M 12/00 (20060101); G04C
10/00 (20060101); H01M 6/50 (20060101); H01M
012/06 () |
Field of
Search: |
;429/27,72 ;58/23,BA
;429/110 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Walton; Donald L.
Attorney, Agent or Firm: Crutcher; William C.
Parent Case Text
BACKGROUND OF THE INVENTION
This is a continuation-in-part of Ser. No. 066,203, filed Aug. 13,
1979 now abandoned.
Claims
I claim:
1. In an air/metal cell of the type having a catalytic
air-consuming cathode disposed in a container and providing a
current flow capacity determined by the rate of flow of air to said
cathode, the improvement comprising;
a chamber connected to admit ambient air to said cell
container,
a barrier restricting flow of air from said chamber to the cathode
for a preselected low current drain on the cell, and
valve means inside the cell arranged to be actuated by an external
force on the cell to bypass said barrier and provide flow of air to
the cathode for a preselected high current drain on the cell.
2. The combination according to claim 1, wherein said cell is a
button cell having a cathode cup defining a portion of said chamber
and wherein said valve means is disposed in said chamber.
3. The combination according to claim 2, wherein said valve means
is adapted to be actuated by force against said cathode cup.
4. The combination according to claim 1, wherein said barier is a
gas permeable membrane supported on a perforated member dividing
said container chamber into two smaller chambers.
5. The combination according to claim 1, wherein said container
includes a bulged out portion operatively connected to said valve
means and adapted to flex and open said valve with an "oilcan"
effect when external force is applied.
6. The combination according to claim 1 including electrical
switching means operatively connected to open said valve means when
the switching means is actuated.
7. The combination according to claim 6, wherein said container
includes a bulged out portion connected to the valve means and
where said switching means presses against the said bulged out
portion to open said valve means with an "oilcan" effect.
8. The combination according to claim 1, including an electric
watch with low current drain powered by said cell, said watch
having a pushbutton adapted to close a circuit to operate a high
current load device in said watch also powered by said cell, said
pushbutton adapted to exert a force on said cell container.
9. In an air/metal button cell of the type having a catalytic
air-consuming cathode disposed in a container including a cathode
cup and providing current flow determined by the rate of flow of
air to said cathode, the improvement comprising:
a chamber defined in said cathode cup, said cup having ports
admitting air to the chamber,
a barrier restricting flow of air to the cathode for a preselected
low current drain on the cell, said barrier including a perforated
member supporting said gas permeable membrane, and
valve means having a valve member in said cathode cup and adapted
to admit air through said barrier providing flow of air to the
cathode for a preselected high current drain on the cell, said
valve being connected to said cup for activation by external force
on the cup.
10. In an air/metal cell of the type having a catalytic
air-consuming cathode disposed in a container and providing a
current flow capacity determined by the rate of flow of air to said
cathode, the improvement comprising;
a chamber connected to admit ambient air to said cell
container,
a barrier restricting flow of air from said chamber to the cathode
for a preselected low current drain on the cell, said barrier
comprising a gas permeable membrane supported on a perforated
member dividing said container chamber into two smaller chambers,
and
valve means comprising a valve member disposed in an opening
defined in said perforated member and connected to a portion of the
cell container and arranged to be actuated by an external force on
the cell to bypass said barrier and provide flow of air to the
cathode for a preselected high current drain on the cell.
Description
This invention relates generally to air/metal cells designed for
low current operation but which intermittently are required to
furnish high current. More particularly, the invention relates to
an improved zinc/air battery useful for a wristwatch connected to
the watch circuit for normal operation and which also
intermittently supplies accessory devices, within the watch, such
as an incandescent lamp requiring a higher current drain.
Air/metal cells are well known in the art, these generally
comprising a consumable metal anode, a catalytic nonconsumable,
oxygen-consuming cathode, and a suitable electrolyte. The
principles of operation of such cells are described in U.S. Pat.
No. 3,419,900 issued Dec. 31, 1968 to Elmore et al and in U.S. Pat.
No. 3,553,024 issued Jan. 5, 1971 to Fishman. Although the
foregoing patents are illustrated in the context of fuel cells or
multicell batteries with replaceable anodes, air/metal cells have
been more conveniently and recently manufactured in the form of
miniature button cells for hearing aids and the like. The typical
zinc/air button cell generally includes the following
components:
1. A cathode can which includes at least one aperture for entrance
of air and which contains a nonconsumable air cathode structure
usually comprising a gas permeable hydrophobic polymer film onto
which is pressed a metal current collection grid and a waterproof,
porous catalyst material such as metal catalyzed activated carbon
admixed with a hydrophobic binder. Although actually an independent
component of the cell, one or more electrolyte-absorbing separator
layers are placed on the catalyst layer of the cathode structure to
separate it from the anode.
2. An anode can which is joined to the cathode can typically by
crimping and which includes a zinc anode mass typically in the form
of amalgamated zinc powder (e.g. containing 3-8 w % Hg) or of a
porous zinc compact, saturated with an alkaline electrolyte such as
a 30-40% aqueous solution of KOH.
3. A polyethylene, polypropylene, nylon, etc. insulator between the
cathode and anode can which insulator also functions in many cases
as an electrolyte seal.
Control of the admission of air to the air-consuming electrode was
provided by small holes in the button cell container as illustrated
in U.S. Pat. No. 3,897,265 issued July 29, 1975 to Jaggard. Such
cells are suitable for relatively high current drains such as 10
milliamperes which are used in hearing aids. Subsequently, zinc/air
cells have been developed for long life, low current drain, as
required in electric wristwatches by adding a special membrane to
control the admission of oxygen to the air-consuming catalyst. One
such type is known in U.S. Pat. No. 4,105,830 issued Aug. 8, 1978
to Kordesch which is permeable to oxygen. Another approach is shown
in U.S. Pat. 4,118,544 issued Oct. 3, 1978 to Przybyla et al using
very tiny pores or passages through a barrier to the cathode.
In all of the foregoing constructions, the means for controlling
the admission of oxygen to the cathode is tailored for a specific
application or range of current drain expected to be encountered by
the cell. The foregoing constructions do not lend themselves to
dual operation of the cell in either a low current or a high
current mode.
In a battery-operated wristwatch, either the digital type or the
analog type (having hands driven through a motor), the watch is
designed to draw very low current from the battery, so as to last
for periods of a year or more. Such watches also typically draw
high currents on an intermittent basis to operate a miniature
incandescent lamp, alarm or similar device. It would be desirable
to have a zinc/air battery to fulfill the functions of low and
intermittent high current drain.
Accordingly, one object of the present invention is to provide an
improved air/metal cell for dual operation either in high current
or low current mode.
Another object of the invention is to provide an improved zinc/air
cell suitable for a battery-operated wristwatch.
Another object of the invention is to provide an improved watch
construction for utilizing such an improved air/metal cell.
SUMMARY OF THE INVENTION:
Briefly stated, the invention is practiced by providing an
air/metal cell, including a barrier restricting flow of oxygen to
the cathode, and having selectively actuated valve means for
bypassing the barrier and admitting a greater flow of oxygen to the
cathode. In the preferred embodiment, the valve means is actuated
by electric switching means closing a circuit requiring greater
current drain on the cell.
DRAWING:
The subject matter, which is regarded as the invention is
particularly pointed out and distinctly claimed in the concluding
portion of this specification. The invention, however, both as to
organization and the method of practice, together with further
objects and advantages thereof, may best be understood by reference
to the following description, taken in connection with the
accompanying drawing, in which:
FIG. 1a is a simplified, cross-sectional, elevation view of a
zinc/air button cell embodying the invention, showing the valve
closed,
FIG. 1b is the same view showing the valve open,
FIG. 2 is a circuit diagram.
FIG. 3 is a simplified cross-sectional elevation view of a
battery-operated wristwatch illustrating a preferred application of
the invention, and
FIG. 4 is a partial cross-sectional elevation view of an alternate
type of wristwatch construction.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIG. 1a of the drawing, a zinc-air button cell is
shown in cross section. Conventional elements include an anode of
compacted zinc or amalgamated zinc powder 1 in an anode cup 2, a
complementary lower cathode cup 3 having, a circular bottom 3a and
cylindrical sidewalls 3b which are crimped around anode cup 2 and
sealed with an insulating grommet spacer 4. The grommet also
includes an annular slot 4a receiving the depending walls of the
anode cup 2. A multilayer separator 5 may be a fibrous cellulose
material which contains aqueous KOH. The cathode 6 may comprise a
layer of activated carbon catalyst coated or mixed with a
hydrophobic polymer such as polytetrafluoroethylene. The cathode 6
is supported on and makes electrical contact with a metallic wire
mesh 16 which also makes electrical contact with the cathode cup 3.
The foregoing materials and constructions are merely illustrative
and not intended to be restrictive of the type of materials or
construction used with the present invention, but are typical of an
air/metal cell.
In accordance with the present invention, a perforated plastic
barrier 7 separates the chamber between the cathode 6 and the
bottom 3a of the cup into two air chambers 8 and 9. The perforated
member 7 serves as a support for air permeable membrane 13 and
includes a plurality of air flow passages 10, the size of which is
not particularly material to the present invention. The perforated
support member 7 includes a central aperture 11 surrounded by an
imperforate portion 12.
An air permeable membrane 13 is disposed on the cathode side of
perforated support member 7 so as to cover perforations 10 and
control the flow of oxygen from chamber 9 to chamber 8. The air
permeable membrane is selected in a manner well known to those
skilled in the art to provide the proper flow of oxygen from
chamber 9 to the oxygen-consuming cathode 6 involved in the
reaction of the cell, so as to control the limiting current which
may be drawn from the cell at its rated voltage. Typical materials
for the air permeable membrane 13 are microporous materials such as
high density polyethylene or unsintered polytetraflouroethylene.
The precise type of air permeable membrane is immaterial to the
present invention and is selected to give the limited current drain
desired for the application. In the case of a wristwatch, this
would be on the order of 7 microamperes.
In accordance with the present invention, the bottom 3a of the
cathode cup includes metering ports 14 which admit ambient air to
the chamber 9. The bottom 3a is constructed to bulge slightly
outward so that external force as indicated by arrow 15 will cause
the bottom of the cup to move inwardly, in an "oilcan" effect, and
become displaced as shown in FIG. 1b.
Attached to the bottom 3a of the cup is a valve member 17. When the
bottom of the cup 3a is in its normal position, valve member 17
closes off the central aperture 11. However, when external pressure
is applied, the valve member opens admitting a greater flow of air
from chamber 9 to chamber 8, as shown in FIG. 1b. When this occurs,
the rate of flow of ambient air to the cathode is controlled by the
area of ports 14 rather than by the air permeable membrane 18.
Ports 14 are selected so that the limiting current flow at rated
voltage is proper for the high current drain device which the cell
is intended to operate.
The operation of the cell should be apparent. In normal operation,
rate of admission of air (oxygen) to the cathode 6 is controlled by
the membrane 13 and is proper for the low current use. For
intermittent high current drain, an external force 15 opens the
valve 17 and the higher rate of flow of air (oxygen) is controlled
by ports 14.
Referring now to FIG. 2 of the drawing, a typical circuit
application of the improved zinc/air cell is illustrated in a
digital wristwatch. The application of external force is associated
with the closing of a circuit by switching means which connect the
cell with a high current drain device, such as the incandescent
backlight for the display in a solid state electronic wristwatch.
FIG. 2 shows a simplified electrical circuit wherein a cell 20 is
connected in parallel circuit configuration with a watch
timekeeping and display load 21 and an incandescent backlight 22.
The watch timekeeping and display circuit 21 is a low current
device which may include a CMOS integrated circuit connected to
cell 20 at all times. Setting switches 23 may be manually actuated
to accomplish such functions as setting the time, date, etc. The
incandescent bulb 22 is a high current device and is selectively
connectable through switching means 24 to the cell. Switching means
24 are also arranged to physically press against the cell when the
switch is closed as indicated by the dashed arrow 25. Thus
actuation of switching means 24 simultaneously connects the high
current device 22 and places cell 20 in a high current drain mode
by enabling additional flow of oxygen to the cathode.
FIGS. 3 and 4 are cross sections of solid state electronic
wristwatches embodying the invention. In FIG. 3, a conductive watch
case 30, caseback 31 and transparent crystal 32 enclose a watch
module which includes a liquid crystal display 33, a backlight
transparent diffuser member 34, integrated circuit 35 and
incandescent backlight 22. The integrated circuit 35 is connected
in circuit with the improved zinc/air cell 36 by suitable leads
(not shown). A pushbutton member 37, which is electrically
connected to the case 30, is arranged to push against an arcuate
spring member 38, which is insulated from the battery by a strip of
insulation 39. Electrical conducting strips 40, 41, serve to
complete the circuit. When the pushbutton 37 is actuated, it closes
the electrical circuit to the incandescent bulb 22, and also causes
the arcuate spring member 38 to physically compress the air cell
36, thus opening the internal valve and placing it in high current
mode to supply the high current consuming device 22. The backlight
illuminates the display 33 by means of the diffuser member 34.
FIG. 4 shows an alternate arrangement of the pushbutton. In this
case, the cell 36 is directly contacted by a flexible conductor 45
which is also grounded to the case. A grounded pushbutton 46
connects the electrical circuit through conductors 47,48 when
actuated. Pushbutton also operates an insulated wedge member 49 to
cause the flexible conductor 45 to press against the cell 36 in a
manner which will be obvious from the drawing.
Thus there has been described an improved zinc/air cell for
intermittent high current demand, which is intended primarily for
parallel operation of a low current consuming device, such as a
typical solid state wristwatch.
While there has been disclosed herein what is considered to be the
preferred embodiment of the invention, other modifications may
occur to those skilled in the art, and it is intended to cover in
the appended claims all such modifications as fall within the true
spirit and scope of the invention.
* * * * *